<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }
        .container{
            width: 100%;
            height: 200px;
            display: flex;
        }
        .left{
            background-color: gold;
            width: 200px;
            height: 100%;
        }
        .right{
            flex: 1;
            background-color: blue;
            height: 100%;
        }
    </style>
</head>
<body>
    <!-- 
        一侧固定，另一个侧自适应
     -->
     <div class="container">
         <div class="left">
             左
         </div>
         <div class="right">
            右
        </div>
     </div>
</body>
</html>